Development of carbon-based catalysts for hydrogen production from hydrogen sulfid
Thesis Type: Doctorate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, -, Turkey
Approval Date: 2025
Thesis Language: Turkish
Student: MERT YEKTA DOĞAN
Principal Supervisor (For Co-Supervisor Theses): Nail Yaşyerli
Open Archive Collection: AVESIS Open Access Collection
Abstract:
This doctoral thesis aims to produce COx-free hydrogen through the decomposition of H2S. For this purpose, sawdust-based activated carbons were synthesized at different carbonization temperatures (800–1000 °C) for a fixed duration of 45 minutes. The performance of these activated carbons and their Fe- and W-loaded forms was investigated in both conventional and microwave reactor systems. Fe-, W-, and Mo- impregnated catalysts supported on commercial activated carbons (CMC1 and CMC2) were also prepared to evaluate the effects of metal type and support. The catalysts were characterized using N2 adsorption-desorption, XRD, SEM, TEM, ICP-OES, elemental analysis, RAMAN, XPS, and TGA-DTA techniques. The AC-T-800-45 sample exhibited an amorphous structure with both micro- and mesopores. Catalytic activity tests were conducted within a reaction temperature range of 400–1000 °C. In the conventional system, activated carbon-supported catalysts achieved higher H2S conversions compared to those supported on CMC1. XPS analysis showed the formation of WS2 in W-containing catalysts and elemental sulfur and sulfate in Fe-containing ones. Online FTIR tests revealed the formation of CS2, CO, and low levels of CO2. Mo addition was found to enhance the catalytic activity of mesoporous carbon-supported catalysts. The AC-T-800-45, AC-T-900-45, and AC-T-1000-45 samples, carbonized at different temperatures, were tested in both reactor systems. As the temperature increased, graphitization and mesoporosity improved, and the highest sp2/sp3 ratio and π–π* transitions were obtained in AC-T-1000-45. This structure enhanced microwave interaction, enabling the target temperature to be reached with lower energy input. At 700 °C, H2S conversions of 13% and 35% were achieved with AC-T-1000-45 in the conventional and microwave systems, respectively, while the theoretical equilibrium conversion was 16%. The higher performance in the microwave reactor was attributed to the formation of “hot spots” within the bed. Overall, sawdust-based, phosphoric acid-activated activated carbons demonstrated high catalytic performance and energy efficiency in both systems.